1. Field of the Invention
This invention relates to a precast concrete pile and to a piling method utilizing the same.
2. Description of Invention
In driving of pre-cast concrete piles, it is conventional to connect a plurality of piles together end-to-end in turn until firm ground has been struck by the lower end of the lower pile, and then to sever off any part of the uppermost pile projecting significantly above the desired level. Such a system is disclosed in, for example, GB No. 783,624. Sometimes, the severed part can be a commercially significant fraction of the uppermost pile, often more than half of the uppermost pile. This severed part may be thrown away. On the other hand, it can be re-used by breaking up the severed end zone and re-casting it with extra reinforcement and with a driving plate transverse to the pile. However, the latter course of action is expensive and time-consuming.
A way of avoiding the expense of waste or of time-consuming work has been proposed in U.S. Pat. No. 2,430,879 and U.S. Pat. No. 4,127,002, in both of which a shell enclosure is mounted atop the uppermost pile co-axially therewith, the column of piles is driven to bearing depth, and the shell enclosure is cut off at a reference terrain level and then filled with a hardenable plastic material, such as concrete.
However, those proposals are disadvantageous in requiring an accurate forecast of the bearing depth, since, if after driving of the shell enclosure, it becomes clear that one or more precast piles should have been added beforehand, the situation can only be rectified with great difficulty, if at all.
In the system disclosed in GB No. 783,624, a reinforced. concrete driving head is either stressed to the uppermost pile section of precast pile sections of a pre-stressed pile, or rests thereupon in the manner of a dolly, the head being removable for repeated use as a driving head. The head bears upon a flat, mild steel ring upon the uppermost pile section, the ring serving as a top end anchoring plate for stressing wires of the pile.